Fig. 1. (a) SOP with known Stokes parameters can be equated to a point on a sphere of radius S0 with coordinates (S1, S2, and S3), or a vector pointing to the point (S1, S2, and S3) from the origin. (b) Length of vector difference between actual and predicted SOP vectors is utilized to describe the error of the system.

Fig. 2. Scheme of the experimental setup for SOP adjustment and speckle collection.

Fig. 3. (a) MPC contains two individually rotatable quarter-wave plates. (b) The speckle patterns with different SOPs are captured by CCD, and the corresponding Stokes parameters are shown under the speckles.

Fig. 4. Structure of CNN mapping SOP to speckle.

Fig. 5. Data set of SOPs with a rotation step size of 20 and covering the entire Poincaré sphere. (a) Distribution of SOPs on the Poincaré sphere. (b) Distribution of RMSEs related to SOPs. (c) The RMSEs corresponding to points in the test set. (d) Comparison of actual and predicted Stokes parameters.

Fig. 6. Data set of SOPs with a rotation step size of 20 covering part of the Poincaré sphere. (a) Distribution of SOPs on the Poincaré sphere. (b) Distribution of RMSEs related to SOPs. (c) The RMSEs corresponding to points in the test set. (d) Comparison of actual and predicted Stokes parameters.

Fig. 7. Distribution of SOP data sets on the Poincaré sphere corresponding to different MPC rotation steps: (a) 1 step, (b) 5 steps, (c) 10 steps, and (d) 20 steps.

Fig. 8. RMSE distribution of SOPs in test sets with different MPC rotation steps: (a) 1 step, (b) 5 steps, (c) 10 steps, and (d) 20 steps.

Fig. 9. Loss of SOPs in test sets on the Poincaré sphere corresponding to different MPC rotation steps. SOPs are randomly selected and do not overlap with the training or validation sets. (a) 1 step, (b) 5 steps, (c) 10 steps, and (d) 20 steps.

Fig. 10. Comparison of actual and predicted Stokes parameters in test data sets with different MPC rotation steps. (a) 1 step, (b) 5 steps, (c) 10 steps, and (d) 20 steps.

Fig. 11. Test data sets include SOPs with a rotation step size of 80, covering the entire Poincaré sphere. The wavelength interval is 0.5 nm with a bandwidth of 10 nm. (a) The speckles with the same SOP of [1.022465, −0.6899, −0.2947, and 0.6608] at different wavelengths. (b) The distribution of SOPs with different wavelengths. (c) RMSEs of SOPs in the test data sets corresponding to different wavelengths.

Table 1. RMSEs of test data sets with different MPC rotational steps.